VAD's are commonly used therapeutic devices and include IV catheters. There are two general classifications of VAD's, peripheral catheters and central venous catheters. If not properly maintained, VAD's can become occluded. To ensure VAD's are used properly and do not become occluded, standards of practice have been developed. These standards include a cleaning procedure, which is commonly referred to as a flush procedure or flushing a catheter.
VAD standards of practice usually recommend flush procedures be performed after catheter placement, before fluid infusion, and before and after drug administration, blood sampling, transfusions and parenteral nutrition. The goal of these flush procedures is to confirm catheter patency, avoid drug incompatibilities, ensure the complete drug dose administration, prevent thrombus formation and minimize the risk of blood stream infections. Flush procedures require different types and amounts of flush solutions. The most commonly used flush solutions are saline and or heparin lock solution. The type of flush solution and amount vary depending on the specific type of catheter. Flush solution volumes between 5 and 10 ml are most common but can range from 1 ml to 20 ml.
For flush procedures, an I.V. line refers to a system containing a VAD, a tubing set with clamp and may terminate with a port or valve. The most common types of ports are covered by pierceable septums or pre-slit septums and are known in the art and sometimes referred to as “PRN” from the Latin pro re nata meaning “as the need arises”. The septum is preferably made of rubber or another elastomeric material, which permits insertion of a sharp needle cannula in order to infuse fluids or to withdraw fluids from the catheter. Upon withdrawal of the needle cannula the septum seals itself. Ports having pre-slit septums are used with blunt cannula or the frusto-conically shaped tip of a syringe barrel. The syringe tip or the blunt cannula (which is usually attached to a syringe) is gently pushed through the pre-slit septum to establish fluid communication.
I.V. valves, another type of terminal I.V. access device that does not require a needle having a sharp tip, are activated by the frusto-conically shaped tip of a syringe barrel to allow fluid communication between the interior of the syringe and the catheter. These valves may contain features for delivering fluid from a storage compartment in the valve to the catheter, and are referred to in the art as positive displacement valves. Such a valve is taught in U.S. Pat. No. 6,206,861.
Flush procedures may be enhanced by use of a “push-pulse” (also referred to as “start-stop” or “push-pause”) technique to remove debris or residue in the catheter that may cause occlusion or other undesirable effects. The removal of debris or residue is referred to a purging and prevents the build-up of deposits of blood, blood residue and IV drugs within a catheter or other VAD device. Such build-up can cause partial or complete blockage of the fluid pathway in a catheter system, require expensive and potentially dangerous methods for purging the affected catheter or a total catheter exchange. Often, such blockages lead to interruptions in therapy that may compromise patient care. The build-up of residue within a catheter can also increase infection risk by providing a breeding medium for microorganisms. For this reason, push-pulse is traditionally taught to healthcare workers.
As is understood by one skilled in the art, the push-pulse flushing technique introduces or creates turbulence within the syringe barrel when uneven pressure or force is applied to the plunger rod in the distal direction as the distal end of the plunger rod moves toward the barrel wall during expulsion. In this disclosure, a convention is followed wherein the distal end of the device is the end closest to a patient and the proximal end of the device is the end away from the patient and closest to a practitioner. When such techniques are used in conjunction with catheters, turbulence is introduced within the catheter. Turbulent or pulsing flow causes a swirling effect that moves any debris or residue attached to the catheter. Turbulent or pulsing flow can be provided in a relatively controlled manner by a syringe that includes a plunger rod that interacts with the syringe barrel as the plunger rod is pushed forward to automatically create sharp pulses in fluid flow and pressure. In contrast to push-pulse and controlled pulsatile flow, conventional or “smooth” (also referred to as “straight” or “laminar”) flushing techniques require the application of substantially constant pressure or force to the plunger rod in the distal direction. Conventional or smooth flushing techniques may also include the application of pressure or force that increases or decreases substantially linearly to the plunger rod in the distal direction. However, the use of features that provide the force differential that creates turbulent or pulsing fluid flow generally cannot be applied with infusion pumps or other delivery systems that require slow and controlled delivery of medication to patients. For example, certain infusion pumps have high pressure alarms and the forces and/or pressures created by push-pulse techniques of flushing can set off the high pressure alarm.
There is a need for a flush syringe assembly that can be used with both manual IV therapies and therapies that use infusion pumps.